1. Field of the Invention
This invention relates to solar absorbers. More particularly, this invention relates to panels or collectors which will absorb heat from the sun and retain it until it is removed by suitable means for use in any of a large variety of ways.
2. Description of the Prior Art
It is well known that solar radiation can be collected by flat plates of metal such as iron, copper or aluminum coated with a black coating. The coating on such a collector is designed to absorb as much of the solar radiation band (wavelengths between about 0.3 and 2.5.mu. ) as possible and reflect as much infrared (wavelengths greater than 4.mu. ) as possible.
One coating which has been experimented with in the prior art is a coating made up of about 0.1.mu. diameter particles of lead sulfide embedded in a matrix of silicone. Such a coating is described in Direct Use of the Sun's Energy, Daniels, Yale University Press, 1964, pp. 209-224. It is reported that such a coating reflects about 10% of the solar radiation band (wavelengths below 2.mu. ) and reflects about 80% of the infrared rays. Therefore, such a coating absorbs about 90% (100% -10%) of the solar radiation band and about 20% (100% -80%) of the infrared. While such figures are admirable, they (particularly the infrared reflectance) do not indicate that such a coating would be suitable for use in a solar absorber. It is desirable to reflect much more (100% if possible) of the infrared and absorb much more (again 100% if possible) of the solar radiation band.